Mettaton Nitro
by CJS51703
Summary: The downfall of Mettaton Neo is his defense. We all know that. Now, with the player killing monsters left and right, Alphys has a plan for Mettaton's fourth form to fix that. (Rated for later.)
1. Chapter 1

*****Hello, everybody! So while I was listening to "Nitro Bot" by Sentai Express, this whole story idea came into my head. Do not worry about background being explained here, because I believe at least a good deal of it is explained within the chapter. Alphys and Mettaton belong to Toby Fox, the story plot belongs to me, and let's jump right in!**

 **Chapter One: What Do You Think?**

"You called for me darling?" Mettaton Classic asked, stepping into his best friend's primary lab. "Y-yes. Please, s-sit down. Over th-there. Stop me if y-you aren't interested in wh-what I'm gonna t-tell you," Alphys permitted, standing in front of a table.

"Okay," Mettaton said. He rolled over to the chair at that table. "...darling, you've got to remember that I cannot sit down in my main form," he deadpanned.

"O-oh...right. I'm s-stupid. Anyways, it's c-c-coincidental that you m-mentioned your form j-just now. You kn-know your three o-ones," Alphys said. "Classic, EX, and Neo. You should know that, you built all of them," Mettaton recalled. Alphys nodded.

"C-correct. W-well, I've been r-re-evaluating your Neo f-form. Its weakness is d-defense. And th-that's on me, I'm s-sorry. But the d-defense is, f-for lack of a b-better word to d-describe it with, c-crap. And with wh-what's been happening l-lately, low defense can b-be your quick d-demise," she said, her voice hushing as she said the last thing. Mettaton hummed, a solemn line of red now across his paneled face.

It had begun to spread across the Underground, by experience or by story, that a human had fallen down. And they were killing monsters left and right.

"So what is it about my form?" Mettaton asked, trying to distract both himself and Alphys. She snapped out of her trance induced by sadness. "O-oh! So, I've c-created some new d-designs for an ever b-better form," she opened. Mettaton's facial panels lit up to show a question mark. "Oh? Tell me more," he inquired.

Alphys grabbed a poster-sized paper that turned out to be a blueprint that had been previously unnoticed on the table. She held it up. "I c-call it, Mettaton N-Nitro," she announced. Mettaton rested on fist on his boxy body. "Again I ask of you, tell me more," he insisted.

"S-sorry. I, uh, g-got excited. Anyways, b-beyond the exterior-b-because I know th-that that matters to you-lie _amazing_ s-stats," Alphys said. She handed over the blueprint, pointing to section detailing stats. Mettaton took the blueprints and looked at that particular section. "30,000 HP, 95 (25) attack, 255 defense," he read.

He looked up from the blueprint an exclamation point on his blocky face. "Darling, these...this is amazing! These stats are much better than my Neo form! Although your handwriting is chicken scratch, to be honest. But that doesn't really matter!" he said. He put the blueprints on the table next to him and barreled straight ahead.

Alphys started scrambling backwards. "D-don't hurt me, don't r-run me over!" she pleaded. Mettaton willed himself to a stop. "Sorry. I got excited and wanted to give you a hug," he said. Alphys moved away from the wall, which her back had slammed into in her attempt to not get mowed down by her own creation. "Y-you can hug m-me. Just...d-don't hurt me," she said.

"Right," Mettaton said. He wrapped his arms tightly around Alphys, who hesitantly hugged back. After a few seconds, they pulled apart. "I-I'm so glad y-you like my idea. I r-really thought y-you wouldn't like it b-because of the a-anime-like design," she admitted.

"For once, your trash cartoons have produced something strong and sleek for me. Good for you," Mettaton said. His panels lit up to show a friendly smile. "S-so, I have th-the necessary pieces th-this project. Sh-shall we begin?" Alphys asked. "Yes," Mettaton replied. "Th-then follow me," Alphys said.

As he followed her, he couldn't help but feel fierce DETERMINATION fill him. He had been Classic, EX, and Neo. Now, he was ready for Nitro.

 *****As for what Nitro form looks like? Don't worry, you'll see that soon. Anyways, be sure to leave a review on the way out, and I'll see you all in the next one! Bye!**


	2. Chapter 2

*****Y'know how, in the description, this story says that it was rated for later? Well, now is later. You've been warned. Alphys, Mettaton, and the fallen human belong to Toby Fox, the story plot belongs to me, and let's get into it!**

 **Chapter Two: Down, Down, Down**

Two weeks had passed since that day. Alphys had put a pin in anything else she'd been working on, dedicating herself solely to working on Mettaton Nitro. She worked all day perfecting Mettaton's new form down to every last screw and bolt.

After she sent him off to recharge, she would watch the fallen human just traipse through the Underground, killing monsters left and right, until she eventually cried herself out and passed out as well. Then, she woke up the next morning by an alarm, downed two cups of coffee, and got Mettaton up before repeating the process once more.

Things were going...decently, in terms of Alphys' health, both mentally and physically. But Mettaton was done at long last in getting his installments. All that was left before he could exercise his new form was a twenty-four hour period of being powered down and covered to his charger. So, that's currently where he was.

Alphys felt a slight sense of relief now that her job was done. She would watch the fallen human's hellish path of choice until she passed out. Then, she would sleep in until she woke up naturally and not with the prodding of her phone's alarm clock and the help of some coffee. She was thinking that would be her plan. But, that wasn't quite the case. Alphys sat down and turned on her console, waiting for the same familiar grief. But she got a different brand of sadness. The fallen human had made it to Waterfall.

Undyne was slowly melting due to her body not being able to handle her high amounts of DETERMINATION. "No...no! Not yet! I won't die!" she screamed, sweat and tears running down her face as she tried to fight her own body. "NGAHHHHHHHH!" She tried to step forward, her breaths shallow and staggered.

Alphys began chewing on her claws in anxiety over what she knew was about to happen. "N-no. Please, n-no," she mumbled as she watched.

Undyne's expression only became more fierce despite the fact that it was melting. "I WON'T DIE! I WON'T DIE! I WON'T DIE! I WON'T!" she insisted in vain. At last, she finally melted and turned to dust. Her SOUL appeared in the open air.

And then, it cracked and fell into pieces.

"About time," the fallen human scoffed. They, they kicked the dust around and moved on. Alphys turned off her console. Silent tears fell down her face and she sat there, frozen in her shock.

When she was able to move once more, she rested her head against her console and sobbed. "N-no, no, no, no, n-no, no, NO!" she said through her cries. When she was done, she curled up on the floor in a fetal position and just laid there.

There were so many things running through her mind in that instant. To help distract herself, she cried out in anger and sunk her claws into her left forearm deeply, dragging them down slowly and jerking them out. It was then that she stood up and knew the way out of this.

She went up to the higher level of her primary lab and grabbed a bottle of chemicals, a piece of paper, and a pencil. She went down to the main area of her primary lab. She looked at the paper, away that the blood from her arm was dripping onto it. She slowly wrote the note, carefully choosing her words and writing in her best penmanship.

Once she was finally through, she put the note and pencil on the desk. She put her glasses on top of them and took the chemical bottle.

"I-I have no idea wh-where I will wake up n-next. But wh-wherever I wake up...M-Mettaton, do me proud. S-stop the human b-before they drag the r-rest of us d-down into h-hell with them," she said. Then, she sighed and went down to the True Lab. _I will die among my mistakes,_ she thought grimly.

Then, she went into the elevator and went down.

 *****I warned you, didn't I? Anyways, be sure to leave a review on the way out, and I'll see you all in the next one! Bye!**


	3. Chapter 3

*****I'm back, my friends. Well...I honestly have no idea as to what to say here. So, Alphys, Mettaton, and the Amalgamates belong to Toby Fox, the story plot belongs to me, and let's get rolling!**

 **Chapter Three: No...**

Mettaton was excited when he powered on. He disconnected himself from his charger and rolled over to the primary lab. He went over towards the escalator leading to the upper level originally. But he stopped cold when he saw something.

A pair of glasses sitting on top of a piece of paper that was folded in half on top of the desk.

A question mark appeared across his blocky face. He picked up the note, immediately unnerved when he saw blood on the paper. He pushed the thousand theories as to why that could've been out of his mechanical mind and began to read the note.

It read as follows:

 _Mettaton,_

 _I had to leave you with something to explain my absence, beyond my glasses, which are to sort of remember me bye. While you spent twenty-four hours powered down, I watched the human keep killing monsters throughout the Underground. They reached Waterfall and murdered Undyne. Although I never got to say my feelings to her, it hurt me just as badly to see her lose her life. When that happened, I knew that everyone who wasn't already dead would soon be dust. As of the time you're reading this, I've committed suicide already. It was nothing you did. It was no one's fault but the human's. I've made so many mistakes already that this was long overdue. I died among my lies and sins._

 _-Alphys_

The note slowly drifted to the floor. Mettaton had dropped it in his shock. "No, no, no, no..." he trailed off. He picked up the note once more and slammed it down onto the desk next to the glasses. He knew just what Alphys meant by mistakes.

So, he went to the secret elevator that appeared to be a bathroom if one didn't know any better. It didn't take but ten seconds perhaps to get down to the True Lab. Mettaton rolled around the Lab faster than ever. What he came across first was the Amalgamate known as Endogeny. "Hello, darling. Where did you last see my dear Alphys? I know what happened to her," he said.

Endogeny solemnly let out an eerie-sounding howl that wasn't quite that of a dog's. He lumbered off further into the Lab. Mettaton followed, assuming that they were going in the right direction.

The True Lab really was a frightening place. It wasn't outright terrifying. But the monotonous hum from devices, dim lights, sporadic creaks and groans, the knowledge of accidently creatures creeping around, and even just the history of the place was enough make one uneasy.

Mettaton was pulled out of his thoughts when he was lead into a particular room. It was a room where old tapes were kept on shelves on both sides of an old, boxy TV with a VCR player hooked up to it. But the other Amalgamates were there in a huddle in the center of the room, letting out saddened...sounds.

Endogeny barked, getting the attention of the monsters of mistakes. They all turned around and expanded their little circle. Mettaton's face lit up in the shape of an exclamation point and he rolled right through.

On the floor were his best friend's remains. Alphys' lab coat, covered in her dust. On top of it was an empty vial with an exclamation point. That meant that it was to be handled with utmost care, and certainly not ingested.

"So she poisoned herself..." Mettaton mumbled. As the other Amalgamates began to wail and whine, he snapped at them all, "SHUT UP!" All of the Amalgamates went silent in an instant. Mettaton's expression became a frown. He didn't dare lay a gloved finger on the pile in front of him.

"None of you are to ever, _ever_ touch this. These are the remains of our darling Alphys. We well never forget her. Now, if you'll excuse me," he said, his voice falling into an angered growl at the end, "I've got something to do."

XxX

It took a little while to navigate to the first room of the True Lab. But Mettaton eventually got back and went up to the primary lab. He turned on the console. The fallen human had made it to the outskirts of Hotland.

"So they passed through here before I woke up and after Alphys committed suicide," he noted to himself. He stepped away from the console. "Well, human, I can beat you to the CORE. I'm faster, stronger, more advanced, and smarter when it comes to navigating Hotland. I'll do this for my fallen friend," he said.

Then, he stormed out of the lab, out for human blood.

 *****Don't worry, things will get quite interesting by the next chapter. Anyways, be sure to leave a review on the way out, and I'll see you all in the next one! Bye!**


	4. Chapter 4

*****Hello, I'm back, and you'll get what I'm deciding to be a challenge in my descriptive writing abilities. Anyways, the fallen human, Mettaton, and Alphys belong to Toby Fox, the story plot belongs to me, and let's jump right in.**

 **Chapter Four: Nitro**

The fallen human jerked their knife out of the last monster in the Core. They turned to dust, crumbling into a pile on the ground. The fallen human looked around.

"Try me! TRY ME! I have faced you all, and I will turn every last one of you to mounds of dust on the ground, never to leave this place again. The taste of your blood is sweet on my blade. If you're still standing, then I will find you and slaughter you all. Your demise is inevitable. So COME ON!" they yelled.

 _But nobody came._

"That's what I thought. Time to end that glorified toaster. He really thought her was something. With -4000 defense, he should really use some common sense. Well, at least he's easy to kill," the fallen human rambled to themselves. They temporarily sheathed their knife and walked forward into the room.

Mettaton was standing there, tube-like arms crossed. "Hello," he said coldly.

"Step aside. Your defense is in the negatives. I've seen what you're made of," the fallen human scoffed. Three dots appeared along the center row of Mettaton's paneled face. "No, you haven't."

He reached around behind him, pressing the button beneath the switch that would've put him into his EX form. "And what's that supposed to mean, you hotheaded microwave?" the fallen human asked. Mettaton laughed to himself. "It means that we're putting on a show that would drive the people wild," he said. And, he began to change.

It only took him a short few seconds for him to full transform. Even the fallen human had to take a step back with widened eyes. "Holy crap," was their response to what they'd just seen.

Mettaton's height had escalated from nearly six feet to just over seven feet tall. His boots were now white, still running up to his knees, now with a sharper point at his heel. His legs were still black, a silver stripe running up the side of his left thigh. His power core heart was no longer pink and jelly-like; it was black and evidently hardened judging by its slight luster. At least, that's what it appeared to be, for his entire midsection was pattered between metal bars and glass. His chest plate no longer had speakers or anything else. It was pure white, with a pixelized outline of a SOUL across it. His once-silver tubed around were now instead slimmer and made of black steel. He wore impressively thick silver gauntlets. Across the tops of said gauntlets were blaster guns. And they were most likely ready to fire. His face was pure white, like his chest plate. His eyes and lips were perfectly black. In his eyes were white slits. His hair was black, short bangs now slightly hanging in his eyes rather than some of his hair sweeping over half of his face. There was a smug smile on his face.

"My darling Alphys thought quite far ahead. Say hello to Nitro," he said proudly.

The fallen human smirked. "Has she already killed herself? She always was a weakling, wasn't she?" they asked. Mettaton's smirk fell into a glare, his perfect teeth bared. "Let's put on a show that will drive them wild," he replied.

And, they went at it.

 *****I will draw Mettaton Nitro (or at least try) in the near future and upload it onto my Undertale Amino page for all of you to see. My username is the same that it is here. And I know that I wrote "the fallen human", and that was because that was the best way I knew to phrase it as. Well, I've got to go take a shower now. So be sure to leave a review on the way out, and I'll see you all in the next one! Bye!**


	5. Chapter 5

*****So good news, I managed to write a few new chapters for stuff since I finished my finals each day with around an hour left in the testing session. So there should be some uploads back-to-back. Anyways, the fallen human and Mettaton belong to Toby Fox, the story plot belongs to me, and let's get on with it!**

 **Chapter Five: My True Power**

The fight had been raging on. The entire room was wrecked to an unbelievable level, whether it be punch marks, lasers, or slashes from a bloodied knife.

"I have to admit, you're good! I thought you'd be as easy as old goat mom. But no, you're as persistent as the overgrown fish stick," the fallen human remarked. They use their sleeve to wipe some blood from their cheek.

"I'm stronger. I'm stronger than both of them," Mettaton growled. He had suffered several dents and was a bit torn up, but he was nowhere near death. And he was even further from giving up.

"It seems so," the fallen human agreed. Although they acted confident, they were a bit nervous on the inside. The fight had gone on for so long and they'd been hit so much that they were fresh out of items. And they had only a low amount of their HP left. Still, they dashed forward, slashing and avoiding Mettaton's attacks, both the ones from his extremities or from his laser guns on his gauntlets.

At last, they had to back out. A wave of dizziness from the blood loss hit them and there were spots in their vision. They shook it off and regained their composure. But they only got to stand there for a few moments.

Mettaton took his opportunities when they were presented to him. When the fallen human had shown even a tad bit of weakness, Mettaton had bolted forward and knocked them onto their back, their knife flying out of their hand in shock of the sudden impact.

The two simply froze in their places. The fallen human was laying on their back. Mettaton pressed his knee into their chest, his expression one of blind fury. The fallen human struggled in a vain attempt to escape.

"Keep struggling, darling," Mettaton said, positioning his gauntlet to where the gun was directly over their forehead, "the audience will _love_ it."

Then, he fired rapidly, shooting ten times at the least. He finally stood up. The fallen human was dead at long last. A glowing red SOUL appeared from their chest. Mettaton took it to where it was safely levitating in his hands.

He started walking towards the Capital. His footsteps were a bit louder in the empty Core. The last place to be ruined by genocide. Mettaton sighed to himself.

"This SOUL is for everyone who last their lives to that human-no, to that _maniac_ ," he decided. He held the SOUL a bit closer, sparing one hand to wipe away a tear of oil before moving it back.

"Especially for you, Alphys."

 **The End**

 *****That would be the end of that. Be sure to leave a review on the way out and I'll see you all in the next one! Bye!**


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